Bug 2502607 (CVE-2026-64062)

Summary: CVE-2026-64062 kernel: netfs: Fix potential deadlock in write-through mode
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in the Linux kernel's network filesystem (netfs) component. Specifically, a vulnerability in the netfs_advance_writethrough() function, when operating in write-through mode, can lead to a system deadlock. This occurs because the function may not consistently unlock memory pages (folios) or mark them as modified, preventing proper writeback operations. Consequently, concurrent memory-mapped (mmapped) read and write operations can cause the system to become unresponsive.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-07-19 17:08:38 UTC 
In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix potential deadlock in write-through mode

Fix netfs_advance_writethrough() to always unlock the supplied folio and to
mark it dirty if it isn't yet written to the end.  Unfortunately, it can't
be marked for writeback until the folio is done with as that may cause a
deadlock against mmapped reads and writes.

Even though it has been marked dirty, premature writeback can't occur as
the caller is holding both inode->i_rwsem (which will prevent concurrent
truncation, fallocation, DIO and other writes) and ictx->wb_lock (which
will cause flushing to wait and writeback to skip or wait).

Note that this may be easier to deal with once the queuing of folios is
split from the generation of subrequests.
Comment 1 TEJ RATHI 2026-07-20 08:16:56 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071911-CVE-2026-64062-a774@gregkh/T